Rocket fuel lines operating according to the bursting principle, which release a flow cross section due to irreversible rupture of material, have been known from a number of publications.
Thus, German Auslegeschrift No. DE-AS 29 13 463 describes a combination of a bursting foil releasing means and a spring-loaded safety valve for securing tanks. etc., against overpressure. The bursting foil arrangement is arranged downstream of the safety valve, and the flow path leads to the atmosphere on the discharge side. The elements are coordinated with one another such that the shearing off of the bursting foil takes place at approximately the same overpressure as the opening of the safety valve against spring force. The bursting foil arrangement in this combination has actually only the task of maintaining the system absolutely tight until the safety valve responds. The fact that the massive rupture disk (called a plate here) clamping the bursting foil is held by a catching device (locking arms) in a positive-locking manner in the shorn-off state after axial displacement can be considered to be an advantageous design feature. A large, defined, low-resistance flow cross section is thus left after a relatively short displacement of the disk.
However, the bursting foil principle described also has drawbacks. As is expressly mentioned in the text, bursting foils tend to form fragments during shearing off. If the flow path formed following the bursting foil leads to further functional elements, such as valves, pumps, nozzles, etc., rather than to the atmosphere, the fragments may lead to serious disturbances and even to system failure. Furthermore, the foils prepared by rolling have relatively great tolerances in terms of their mechanical properties (breaking strength, breaking elongation, etc.), depending on the degree of deformation during manufacture. The incalculable internal stresses generated in the process are also disadvantageous. The clamping of the foil between massive components leads to additional internal stresses, so that the bursting parameters (pressure difference, deformation, etc.) will ultimately have relatively great dispersions. For reasons of tightness, the foils are usually welded to the massive components, as a result of which internal stresses and internal deformations will additionally develop. This makes it clear that a relatively exactly calculable rupture behavior cannot usually be achieved with bursting foils.
Bursting foils usually also have low resistance to aggressive media, and the structural changes and internal stresses resulting from the high degree of deformation have an unfavorable effect. In the case of designs with welded foil, the weld seams, which are correspondingly small, represent areas with especially high risk of corrosion. Finally, it should also be mentioned that the bursting foil arrangement according to the Auslegeschrift in question inherently facilitates the local corrosive attack due to the double-sided notching, which inherently results from the design.
German Patent No. 24 27 790 describes a release valve for pressure tanks, which can be triggered by an explosive force. The element (rupture plate) to be destroyed is separated here in the area of a reduced cross section by igniting a circumferential hollow charge. Since the destruction is brought about here by the explosive force rather than by the inner pressure in the tank, it is possible to use relatively great wall thicknesses, which are unproblematic with respect to corrosion, and the properties of the material of the rupture element also play a less significant role. This is contrasted by the drawbacks that such a solution is absolutely unsuitable in connection with inflammable and explosive media, e.g., rocket fuels, and, in addition, it generates extreme contamination (fragments, remnants of explosive, etc.) in the system.
U.S. Pat. No. 3,842,598 describes a rocket engine for military missiles, which is designed for being able to be stored for a long time and for readiness in a short time. A large part of the volume of the fuel tank is filled with an essentially liquid mixture of a fuel with low oxidant content and an oxidant. It also contains a flexible, sealed tank with additional oxidant. The flexible container is caused to burst in the case of use by means of a pressurized gas (nitrogen) from another tank, and the oxidant released is distributed in the fuel mixture, as a result of which a high-energy, stoichiometric fuel is formed. It is burned in a downstream thrust chamber.
One bursting membrane each is arranged between the pressurized gas tank and the fuel tank as well as between the fuel tank and the thrust chamber for reasons of hermetic sealing during the phase of storage, but no information is given concerning the design of these bursting membranes.
A valve with a bursting element for a rocket fuel system, which is installed in addition to the isolation valve proper, has been known from U.S. Pat. No. 3,714,777. The fuel (here: oxidant) is pressed out of the tank by means of pressurized gas via a tight, flexible membrane or expulsion bladder. If the pressure difference between the pressurized gas and the oxidant is too high, the membrane may be destroyed, and pressurized gas will unintentionally enter the fuel system. The said additional valve regulates the pressure difference to an allowable maximum by automatically throttling the oxidant flow to a variable extent. The bursting element is destroyed by the oxidant pressure at the beginning of the phase of operation, and it releases a pressurized gas line for the control process.
The drawbacks explained at the beginning, such as inaccurate response behavior, disturbances in operation due to fragments, etc., also apply to the designs known from these U.S. patent specifications.